Display screen or portion thereof with a graphical user interface



The FIGURE is a front view of a display screen or portion thereof with graphical user interface, showing our new design.

The dashed broken line showing of the device and portions of the graphical user interface are included for the purpose of illustrating environmental structure and portions of the graphical user interface that form no part of the claimed design.

The dash-dot broken line showing of the display screen and portions of the graphical user interface in the figure represent the bounds of the claimed design and form no part thereof. 

CLAIM The ornamental design for a display screen or portion thereof with a graphical user interface, as shown and described. 